4,577 research outputs found
Spontaneous two photon emission from a single quantum dot
Full text linkSpontaneous two photon emission from a solid-state single quantum emitter is
observed. We investigated photoluminescence from the neutral biexciton in a
single semiconductor quantum dot coupled with a high Q photonic crystal
nanocavity. When the cavity is resonant to the half energy of the biexciton,
the strong vacuum field in the cavity inspires the biexciton to simultaneously
emit two photons into the mode, resulting in clear emission enhancement of the
mode. Meanwhile, suppression was observed of other single photon emission from
the biexciton, as the two photon emission process becomes faster than the
others at the resonance.Comment: 13 pages, 4 figure
Suzaku study of gas properties along filaments of A2744
Full text linkContext: We present the results of Suzaku observations of a massive galaxy
cluster A2744, which is an active merger at . Aims: By using long
X-ray observations of A2744, we aim to understand the growth of the cluster and
the gas heating process through mass accretion along the surrounding filaments.
Methods: We analyzed data from two-pointed Suzaku observations of A2744 to
derive the temperature distribution out to the virial radius in three different
directions. We also performed a deprojection analysis to study radial profiles
of gas temperature, density, and entropy and compared the X-ray results with
multi-wavelength data to investigate correlations with the surface density of
galaxies and with radio relics. Results: The gas temperature was measured out
to the virial radius in the north-east region and to about
in the north-west and south regions. The radial profile of the gas
temperature is rather flat and the temperature is very high (even near
); it is comparable to the mean temperature of this cluster (
keV). These characteristics have not been reported in any other cluster. We
find a hint of temperature jump in the northeast region whose location
coincides with a large radio relic, indicating that the cluster experienced gas
heating because of merger or mass accretion onto the main cluster. The
temperature distribution is anisotropic and shows no clear positive correlation
with the galaxy density, which suggests an inhomogeneous mass structure and a
complex merger history in A2744.Comment: 8 pages, 8 figures, A&A accepte
Suzaku observations of the low surface brightness cluster A76
Full text linkContext: We present results of Suzaku observations of a nearby galaxy cluster
A76 at z=0.0395. This cluster is characterized by extremely low X-ray surface
brightness and is hereafter referred to as the LSB cluster. Aims: To understand
the nature and thermodynamic evolution of the LSB cluster by studying the
physical properties of the hot intracluster medium in A76. Methods: We
conducted two-pointed Suzaku observations of A76 and examined the global gas
properties of the cluster by XIS spectral analysis. We also performed
deprojection analysis of annular spectra and derived radial profiles of gas
temperature, density and entropy out to approximately 850 kpc (~ 0.6 r_200) and
560 kpc (~0.4 r_200) in A76 East and A76 West, respectively. Results: The
measured global temperature and metal abundance are approximately 3.3 keV and
0.24 solar, respectively. From the deprojection analysis, the entropy profile
is found to be flat with respect to radius. The entropy within the central
region (r < 0.2r_200) is exceptionally high (~400 keV cm^2). This phenomenon is
not readily explained by either gravitational heating or preheating. The X-ray
morphology is clumped and irregular, and the electron density is extremely low
(1e-4 -- 1e-3 cm^-3) for the observed high temperature, suggesting that A76 is
in the early phase of cluster formation and the gas compression due to
gravitational potential confinement is lagging behind the gas heating.Comment: 7 pages, 5 figures, A&A accepte
X-Ray Study of the Outer Region of Abell 2142 with Suzaku
Full text linkWe observed outer regions of a bright cluster of galaxies A2142 with Suzaku.
Temperature and brightness structures were measured out to the virial radius
() with good sensitivity. We confirmed the temperature drop from 9 keV
around the cluster center to about 3.5 keV at , with the density
profile well approximated by the model with . Within
0.4\r_{200}, the entropy profile agrees with , as predicted by the
accretion shock model. The entropy slope becomes flatter in the outer region
and negative around . These features suggest that the intracluster
medium in the outer region is out of thermal equilibrium. Since the relaxation
timescale of electron-ion Coulomb collision is expected to be longer than the
elapsed time after shock heating at , one plausible reason of the low
entropy is the low electron temperature compared to that of ions. Other
possible explanations would be gas clumpiness, turbulence and bulk motions of
ICM\@. We also searched for a warm-hot intergalactic medium around
and set an upper limit on the oxygen line intensity. Assuming a line-of-sight
depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an
overdensity is calculated to be 280 or 380, depending on the foreground
assumption.Comment: 14 pages, 8 figure
ISTIHSAN (Telaah Sosiologi-Kultural Pemikiran Imam Hanafi)
Full text linkTulisan ini adalah upaya untuk mengeksplorasi pemikiran fikih Abu Hanifah dengan menggunakan kacamata sosiologis. Pemikiran seorang tokoh tidak lahir dengan sendirinya, tanpa peran serta kondisi social, politik dan budaya yang berkembang pada masa tokoh pemikir tersebut hidup. Karenanya, pemikiran Abu Hanifah tentang Istihsan juga tidak bisa dilepaskan dari kondisi dan struktur masyarakat Kufah, sebagai basis dan tempat tinggal Imam Abu Hanifa
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